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Porter Cable BSV 750-W Brushless Generator with NO AC output

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Registered

Okay. So I guess I will test the diodes first along with the resistors.

But do any of you know if the idea of putting 12 VDC on those red wires going to the CAP is a good thing or bad thing? Looking back at Jim Rankin's post I'd thought he was referring to the wires going to my CAP.
Thanks,
Joe

Lead Head

Guest

That capacitor looks like an oil filled capacitor, and generally those are only used on AC. I would not put DC across that.

I believe way these brushless sets work, is there is a winding in the generator head that induces an AC current into the rotor. The diodes in the rotor than rectify that AC current into DC, basically turning the rotor into a big magnet with a North and South pole. That unchanging magnetic field then induces an AC current back into the main power winding in the stator.

I'm not entirely sure how they regulate, however.

What I would try doing (if possible) is applying 12v to the rotor windings briefly (with the engine off course). You will need to get the polarity right otherwise current will not flow. That might give the rotor just enough magnetism to start generating on its own once started.

Registered

First is an exciter field. This is a stationary steel ring with a winding fed by 2 leads. The exciter/regulator system feeds DC power into this field

Next is the exciter armature, this is a steel ring with windings that rotates inside the exciter field. The windings may be single phase with 2 leads out to the rectifier or 3 phase with 3 leads out to the rectifier. The exciter armature makes AC power which must be rectified to DC

The rectifier may be discrete diodes on heat sinks or a packaged diode 'bridge", but it converts the AC power produced by the exciter armature into DC which powers the main alternator rotating field.

So, three components to replace the brushes and sliprings.

To flash the field/restore residual, you can introduce DC voltage into the exciter field leads, matching + and - (because the exciter/regulator system will operate on a specific polarity when it begins to get enough feedback voltage to work with)

Other methods of flashing, (drill, 2 bulb suicide cord, large magnet stuck to the outside of the generator) depend on creating some current flow in the AC stator in the hope that with the generator field rotating, there will be some magnetic field produced that can be "cut" by the field windings and create some power...which creates more current flow......which creates more magnetic field strength......etc etc....

To answer your question........the exciter cap will be on the AC side of the exciter/regulation system, you need to apply DC power to the leads feeding the exciter stationary field. There will be a rectifier somewhere on the frame of the generator that makes this transformation from AC to DC. Find it and check that it feeds the exciter stationary field (2 wires, + and -)

Are you sure that applies to the OP's 'capacitor' regulated set? As far as I can see, there is no DC fed to the stationary winding. These capacitor regulated sets are a bit strange, and I'd like to find a good technical description of how they operate, but from what I've seen they differ from the conventional brushless sets you're describing.

I've never tried putting DC on the stationary 'exciter' winding on a capacitor-regulated set, so I may be totally off-base here...

(I do have one of these, maybe this would be a good science experiment...)

Registered

You will find a variety of suggestions on flashing if you search this website, and some may disagree with this method.

A generator repair shop once told me that the correct way to flash a brushless capacitor-regulated generator, was to apply DC across the capacitor.

You would do it by momentarily touching your battery's leads across the capacitor while the engine was running. If successful, there would immediately be an AC voltage across the capacitor, so you need to be careful.

It might be a good idea to put a One Amp fuse in series to be sure you don't damage the generator winding or the battery. Someone suggested that a 9 Volt transistor radio battery would work.

Registered

Are you sure that applies to the OP's 'capacitor' regulated set? As far as I can see, there is no DC fed to the stationary winding. These capacitor regulated sets are a bit strange, and I'd like to find a good technical description of how they operate, but from what I've seen they differ from the conventional brushless sets you're describing.

I've never tried putting DC on the stationary 'exciter' winding on a capacitor-regulated set, so I may be totally off-base here...

(I do have one of these, maybe this would be a good science experiment...)

You're ahead of me on this question Jim. I don't own one and have never looked into one with a capacitor regulation system. I am assuming the capacitor is on the AC stator auxillary winding side of a rectifier which creates DC to feed into the exciter field (stationary winding). Could be on the DC side to smooth out ripple??

If there is no rectifier between the auxillary stator winding (AC output) and the brushless exciter stationary field, I suppose it is possible to effectively create a rotary AC transformer between the stationary field and the rotating armature as long as the resulting DC power input into the main alternator field is somewhat proportional to the load of the AC stator lines.

Lead Head

Guest

Registered

I was responding to last para of post 27"there is no rectifier between the auxillary stator winding (AC output) and the brushless exciter stationary field,.."

Yes, the rectifiers and bleed resistors are on the end of the rotor, so the rotor windings get 1/2 wave DC.
I was confirming no rectifier visible in stator exciter winding circuit, just a capacitor. That makes me think the stator exciter windings have AC current with a leading power factor.

The DC magnetic field in the rotor induces AC voltage in the stator main and exciter windings. They are on a common core, so as the load on the main windings increases, the magnetic field becomes stronger, and the current in the exciter windings increases.

More excitation increases the rotor magnetic field, increasing main winding current and voltage. The rate of change is determined by exciter winding and capacitor size. Output is limited by core saturation. -- That is the way I think it works.

Registered

WOW! This is getting over my head real fast. I want to test the diodes as some of you are now realizing might in fact be the exciter field windings that are on the rotor. To be honest with everyone, it looks daunting to try and unsolder the diodes on the rotor without actually taking the end of the genset off. There appears to be 4 long screws that hold the outer shell and the end with the rotor bearing all together. (I have looked at Porter Cable's website for some bogus information) If I take the 4 nuts off of these long screws and then take the big nut off the rotor shaft I think I can see and get to the rotor diodes better and unsolder so I can actually test them to see if they are good or not.
If you can zoom in on the pic with the CAP out of the way, this is the 1st pic attached. You can actually see the diode under the frame attached to the winding on the rotor. There are 2 of these that are 180 degrees opposite of each other.
In the 2nd pic you can see the diodes opposite of each other and the CAP back in its position with wires attached.
In the 3rd pic you see 4 wires coming out of a winding that appears to be part of the stator windings. There are 2 yellow wires that go to the bridge rectifier that is mounted to the frame. The DC wires on this bridge rectifier go straight to a set of test pins on the genset's front panel for having 12VDC if you should need it for something. The other 2 wires in the pic next to my hand are white and they go directly to the Idle Control Assembly board mounted inside the wiring compartment of the front panel for the outlets and starter switch with the breakers and all.
The 4th pic is the Idle Control Assembly PC board. It appears to okay. From what I can tell it gets power from the white wires and passes it to a solenoid on the carbureator for when you have the Idle control turned on. I don't know what the power on the white wires is supposed to be and I don't read any with a volt meter.
Still trying to figure it all out.
Thanks for helping.
Joe

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Registered

Yours has an idle control board. Mine does not. Mine is a contractor's model and has mechanical governor. Pull start, no battery.
I do not have the service manual for mine, just operating manual.

A lot of generator service manuals say to support the rotor when taking it apart. Apparently, the weight hanging off the front bearing can cause shaft to bend.

I pulled the stator off mine to clean everything. I drained fuel and oil. I put down a folded mattress pad, and while it was in frame, solidly blocked the unit and stood it on front end. I removed end bell, bearing, stator. By bracing the unit so the shaft stayed vertical, I did not have to worry about supporting the rotor while removing/ reinstalling the stator. Since the rotor was good - just a little rust to clean and coat, I saw no reason to remove it.

Maybe you could do this to remove the end bell to check diodes & resistors, and avoid pulling rotor. Easier to desolder diode connection in that position.

Subscriber

I've never tried this, but somewhere I read that a quick blip on the throttle to get the set running faster than 3600 rpm can sometimes help. Assuming the set has almost enough residual magnetism, this could give it a bit if a push to get it over the hump and start generating.

But now I'm curious. If this set has auto-idle, what rpm is the engine running at?

Registered

Sorry everyone that may be following this thread for my delay. I've been busy researching and testing in between and working 60+ hrs a week. I brought home a tach light onle to find out it didn't work. I still have not unsoldered the diodes but I found 2 real good websites that I think will lead me to the final analysis of what's not right with my generator. http://www.gillettegenerators.com/files/support/PORTABLE_Srvm3-20120823.pdf
This company has a generator that is almost identical to mine. It is a service manual that describes 10 easy steps in troubleshooting a "powerless" "brushless" generator.
Many of your suggestions are in this service manual in a prioritized order. Not only that but they have readings and explanations with illustrations that really helps a guy that has never done any work on a genset, like me.
I have not had a chance to follow their steps but when I do I will keep this forum informed as to which step brought the genset back to life.
I know it is bothersome for people to find the answer they are looking for and then when they get it, not share it with others. Arrrgh.
This guy actually had the electrical diagram for my particular model.http://members.rennlist.org/warren/portercable7500.pdf
Stay tuned more to come in days ahead.
Joe

Registered

Test Results as of today.
I finally got around to testing some more.
I checked the speed of the motor with a digital strobe light. It was around 3550 RPM. That is well within its range of 3600 RPM. That's less than a 2% difference. I don't think speed is a concern.
I unsoldered the 2 diodes from the rotor excitation windings. The VOM was placed on the diode setting. In one direction with the common lead of the VOM on the striped side of the diode and the positive lead on the other side it passed about .455 VDC. With the leads switched the meter reads O.L.. This reading was done with both diodes and both had the same results.They tested GOOD using the VOM.
I noticed there was a resistor soldered in parallel with the diodes on both of the windings. I tested the resistors and they both read about 9.7Kohms. I'm not sure why they have resistors in parallel with the diodes but it is what it is.
So I believe the diodes are good too.
I checked the exciter windings and both have about .4 ohms resistance on both windings with no short to ground.
I checked the windings from the CAP and they measured about 1.9 ohms. No shorts to ground on the CAP windings.
I checked the windings of the stator and both sets measured about .4 ohms. No shorts to ground on the stator windings.
I followed the directions from the link above and tried to re-excite the residual magnetism on the stator exciter which is connected to the CAP (if I'm understanding those instructions) using the method of striking the cap with 12VDC just for a second and this did not seem to make a difference.
To recap....
I've tested everything independent of other components. CAP, diodes, windings, speed. I still have nothing. I even tried using the 3 lights in series with 2-100W and 1-150W light bulbs in case the last test I did with the 3-4W bulbs were not enough wattage to make a difference. Still no voltage.
I know some of you recommended me not putting 12VDC to the CAP wires but as the manual said in the link above, I did and it did not make any difference.
I tried using the drill method and had no luck. Again, not sure if it was the drill or the gearing in the drill as the drill I was using was a very slow speed drill.
I was wondering, if the 3 lights in series works does anyone know how long this process should take? 5 mins? 10 mins? Longer? Any ideas?
So for now, I'm stumped. I'm going on vacation next week so I won't be commenting from my troubleshooting views but if you still have any input please don't hesitate to share.
Joe

Registered

Again, I would ask this question.
Are you referring to the 2 wires that connect to the CAP? Or the AC side of the bridge rectifier that seems to serve the 12VDC posts on the front of the panel as I described earlier?

Some suggest just putting this 12VDC on for a split second. Do you think that is correct? Or should I let it lay on there for say 4-5 seconds?

I called Porter Cable tech services here in Indianapolis and told the tech guy I was an electrician and he spilled his guts. He said "we don't usually give this information out but you sound like you know what you're doing" LoL

He gave me the ohms values for the stator windings (both sets orange to black and red to green .130-.145 ohms), rotor windings 1.43-1.53 ohms, pink or red wires to CAP .950-1.2 ohms.
I told him I had around .4 ohms on the main windings and he said that sounded okay.

He then told me to flash the pink wires disconnected from the CAP with the 12VDC battery . He did not say whether I should have the motor running when I do this or have it off. I'm not sure how I missed that bit of info. :shrug:

Registered

Flashing can be done with the engine stopped if everything is functioning properly so that the resulting residual magnetic field will produce enough voltage when the set is started up.

If flashing with it stopped doesn't work, try flashing with the generator spinning at rated rpm/frequency. With the field wires attached to the terminal board, I would flash for just a few seconds at a time, observing correct polarity. This can sometimes kick one off that would not otherwise build up from flashing while the engine is stopped. The ones that behave like that usually have some sort of minor problem or are designed that they need flashing every time.

If this doesn't result in buildup of full voltage, then disconnecting the field wires and attaching them to a battery (with the engine running) can provide some information about the integrity of the main generator components. If your generator doesn't put out a stable AC voltage when you supply the field with a source of DC power, something is wrong with one of the major components.

I haven't personally used a synchronizing or 2 bulb cord connecting the generator AC output to another AC source. However, this should work nearly instantly if it is going to work. The 2 bulbs are required because the maximum voltage difference between 2 unsynchronized AC sources is 2X the normal voltage (assuming you use equal voltage rated generator and supplemental AC sources). As the two voltage wave forms synchronize, the lights go out but as they drift away from synchrony, the voltage differences increase.

If the lights only glow steadily, the generator is not making any voltage and the generator winding is simply completing the circuit through the lamps which is supplied by the supplemental source. If the lamps flicker, there is some voltage being produced by the generator.

L

Lead Head

Guest

Again, I would ask this question.
Are you referring to the 2 wires that connect to the CAP? Or the AC side of the bridge rectifier that seems to serve the 12VDC posts on the front of the panel as I described earlier?

Some suggest just putting this 12VDC on for a split second. Do you think that is correct? Or should I let it lay on there for say 4-5 seconds?

I called Porter Cable tech services here in Indianapolis and told the tech guy I was an electrician and he spilled his guts. He said "we don't usually give this information out but you sound like you know what you're doing" LoL

He gave me the ohms values for the stator windings (both sets orange to black and red to green .130-.145 ohms), rotor windings 1.43-1.53 ohms, pink or red wires to CAP .950-1.2 ohms.
I told him I had around .4 ohms on the main windings and he said that sounded okay.

He then told me to flash the pink wires disconnected from the CAP with the 12VDC battery . He did not say whether I should have the motor running when I do this or have it off. I'm not sure how I missed that bit of info. :shrug:

I was talking about the AC side of the bridge rectifier, since that will naturally be low-voltage anyways.

But if the generator guy said to flash it with the cap wires, I suppose I'd try that. With the engine off, there will be about 12 amps of current going through the capacitor windings if you hook a battery directly to it. I wouldn't connect it for more than a few seconds.